Polarization Dependence of Phonon Induced Desorption of He Atoms at Low Temperatures

We directly observe the desorption of He atoms from a thin film on the surface of a solid by both longitudinal and transverse ballistic phonons. Ballistic propagation of the He atoms, sound in the vapor and second sound in the bulk liquid are all separately observed. Comparison of the data reveals that the efficiency of conversion of L and T phonons is the same for these three different modes of coupling.